Describe

Describing a Table

To view the schema of a table, use DESCRIBE TABLE or SHOW TABLE followed by the table name. Without the TABLE keyword, a name after SHOW is read as a setting, not as a table (see SHOW).

SQL

CREATE TABLE tbl (i INTEGER PRIMARY KEY, j VARCHAR);
DESCRIBE TABLE tbl;
SHOW TABLE tbl;

 column_name | column_type | null | key  | default | extra
-------------+-------------+------+------+---------+-------
 i           | INTEGER     | NO   | PRI  | NULL    | NULL
 j           | VARCHAR     | YES  | NULL | NULL    | NULL

 column_name | column_type | null | key  | default | extra
-------------+-------------+------+------+---------+-------
 i           | INTEGER     | NO   | PRI  | NULL    | NULL
 j           | VARCHAR     | YES  | NULL | NULL    | NULL

Describing a Query

To view the schema of the result of a query, prepend DESCRIBE to a query.

SQL

DESCRIBE SELECT * FROM tbl;

 column_name | column_type | null | key  | default | extra
-------------+-------------+------+------+---------+-------
 i           | INTEGER     | NO   | PRI  | NULL    | NULL
 j           | VARCHAR     | YES  | NULL | NULL    | NULL

Using DESCRIBE in a Subquery

DESCRIBE can be used as a subquery. This allows creating a table from the description, for example:

SQL

CREATE TABLE tbl_description AS SELECT * FROM (DESCRIBE TABLE tbl);

Describing Remote Tables

It is possible to describe remote tables over HTTP(S) and S3 using the DESCRIBE TABLE statement. For example:

SQL

DESCRIBE TABLE 'https://example.com/data.csv';

 column_name | column_type | null | key  | default | extra
-------------+-------------+------+------+---------+-------
 a           | BIGINT      | YES  | NULL | NULL    | NULL
 b           | VARCHAR     | YES  | NULL | NULL    | NULL
 c           | DOUBLE      | YES  | NULL | NULL    | NULL